A number of different types of apparatus have been developed to satisfy the increasing demand for cryogenic refrigeration. These devices, all based upon the controlled cycling of an expansible fluid with suitable heat exchange to obtain refrigeration, are exemplified by U.S. Pat. Nos. 2,996,034, 2,996,035, 3,274,786, 3,333,433, 3,312,239, 3,321,926, 3,625,015, 3,673,809, 3,717,004, 3,733,837, 3,788,088, 3,802,211, 3,884,259, 4,036,027, 4,078,389 and 4,118,943, the prior art cited in those patents, and British Pat. No. 1,352,153.
The present invention is directed to an improved form of refrigeration system suitable for performing the refrigeration cycle described in U.S. Pat. Nos. 2,996,035 and 3,625,015.
The refrigeration cycle of U.S. Pat. No. 2,996,035 requires that a high pressure fluid be introduced into a "warm" chamber and flow along a heat storage path into at least one "cold" expansion chamber of variable volume, with the volume of the latter chamber being varied by movement of a displacer and the fluid being discharged at a low pressure into a low pressure fluid reservoir or into the inlet of a compressor. In such a cycle, the control of fluid flow and movement of the displacer must be continuously and accurately timed, with the action of the valves controlling the fluid flow being appropriately coordinated with movement of the displacer.
In the apparatus of U.S. Pat. No. 3,625,015, reciprocal movement of the displacer is achieved by a mechanical driving means, while the valving controlling the fluid flow is achieved by a rotary valve which is mechanically linked to the drive means for the displacer.
While the rotary valve arrangement is reliable, it is relatively complicated and is interposed between the Scotch yoke crank which drives the displacer and the main drive shaft which couples the Scotch yoke crank to the electric motor which serves as the prime mover for the refrigerator.